Today more and more people use the possibility to connect their home computer to the employer's intranet to be able to work from home. The companies often provide their employees with a possibility to connect to the company's intranet via the company's Private Branch Exchange (PBX). The connection is generally established by means of the employee calling the exchange, using his home computer and a modem, and then after a successful identity check, the user is permitted access to the intranet, and a data connection is set up between the user's computer and the intranet, through the exchange.
The international application WO98/44701 describes a device and a method for connecting a computer to a data network via an exchange. The exchange is equipped with a network connection device that sets up the connection between the computer and the data network. At the establishment of the connection, a network address, belonging to the network connection device, is associated with the computer, or more exactly with the telecommunications connection to which the computer is connected.
In order to make it possible for a person with a single telephone line, to have his computer connected to a data network, via the telecommunications network, and at the same time utilize the service telephony, a number of technologies have been developed. An example of such a technology is IP-telephony, wherein speech signals are sent over the data connection in packets, which follow the IP (Internet Protocol) protocol standard. IP-telephony may be performed by means of a so-called IP-telephone or by means a computer provided with an IP-telephony application. An exchange that supports both normal telephony and IP-telephony generally has special telephone numbers for IP-telephony (hereafter called IP-telephony numbers), which are used when setting up IP-telephony phone calls. The IP-telephony number is a normal extension number that is associated with an IP-address (and possibly also with a port number) that has been assigned to a session of an IP-telephone or an IP-telephony application of a computer. The association is made when the session is activated. When an IP-telephony number is called the call will thus be directed to a certain IP-address rather than to a fixed telecommunications line as is the case when a normal telephone number is called. The exchange will further know that a call placed to the IP-telephony number is to be forwarded to an endpoint in IP-packets, instead of as a normal call in time slots. The IP-telephone or the IP-telephony application may be connected to the company exchange through a dial-up connection, e.g. a PPP connection.
In a variant of IP-telephony the exchange is provided with a special telephony server. A user who is connected to a computer network by dial-up may divert calls placed to his own telephone number so that they are directed to the telephony server instead of to his telephone. The call diversion is usually activated from the user's telephone before he connects to the computer network. The telephony server is able to convert time slot speech information into IP-packets and send these to the user's computer over the existing data connection. The user will then use the computer instead of an ordinary telephone to place and receive telephone calls while he has his computer connected to the data network. The computer will, for this purpose, have to be provided with a telephony application, which inter alia handles communication with the telephony server. The telephony server stores information regarding which diverted telephone number is to be associated with which data connection so that calls that are diverted to the telephony server reach the right user.
The international patent applications WO 97/18622 and WO 98/10573 both describe techniques for a user who is connected to a data network to use the service telephony on the same telecommunications line that is used for the data connection.
When a user has connected his computer to the data network, as described above, via the telephone network, and at the same time has made arrangements to use one of the techniques described above to be able to place and receive phone calls on the same telecommunications line that is used for the data connection, so-called “trombone” connections often arise. In a trombone connection several trunk channels are used unnecessarily to set up a connection that could be set up with a single trunk connection. A trombone connection may for instance arise when a user who is working at home and for that reason has diverted calls placed to his office telephone number, which is an extension number in the exchange, to his home telephone number, in order to be able to receive his office phone calls at home. However, when the user connects his computer to the office data network, through his single telephone line, via the exchange, a call that is placed to the home phone number will meet a busy tone, unless the user has diverted his telephone and activated one of the services for receiving phone calls while he is connected to the data network. When the user has performed the necessary steps for using such a service for receiving phone calls over the data connection, calls to his home phone number will be diverted to e.g. an IP-telephony number in the exchange or a number of a telephony server of the exchange. With this arrangement a call that is placed to the user's office telephone number in the exchange will first be diverted and routed over a first trunk channel to a local exchange that has the user's home telephone number as one of its extension numbers. The local exchange holds the information that the user's home telephone number is in turn diverted to the IP-telephony or telephony server phone number in the exchange, so that the call then is routed back to the exchange over a second trunk channel. In the exchange, the call is converted into packets and then again redirected and sent over the data connection in use, in a third trunk channel already occupied by the data connection, back to the user's local exchange and then to the user's home. This is obviously an undesirable type of connection and an inefficient use of available trunk channels.